Even though it's all unfinished, I think that the songs MJ made in his last years could be the best era of MJ's unreleased work. Most of the songs from other eras weren't released/finished because of MJ not thinking the songs were good enough, feeling like there was something else he could've added to them or because it was left out due to better songs taking the spot. But from that era everything was left unfinished and unreleased because he died, not because of their quality.
I'm not speaking with certainty since we barely heard any songs from that era, but judging from the few that released/leaked, from Damien's words it could be considered the best era of MJ's work, if you don't mind the songs not having vocals or being extremely unfinished.